Process for safe storage, handling, and use of acetylene

ABSTRACT

Acetylene and ethane are blended to form mixtures that are safe toward deflagration under any conditions of compression. The blends are then compressed and condensed to form liquids that can be safely stored, transported, and used as a source of acetylene in chemical reactions.

United States Patent 1191 Walker Jan; 21, 1975 [541 PROCESS FOR SAFE STORAGE, 1,528,765 5/1923 Harris 4x/197 FM DLIN AND USE O ACETYLENE 1,528,766 5/1923 Harris 48/197 FM 3,150,495 9/1964 Reed 1 1 1 62/54 Inventor: Davld Walker, x/t Tex. 3,706,542 12/1972 Gilks 48/197 FM Assigneez Tenneco Chemicals, Inc. Saddle 3,713,793 l/l973 Maruyuma et ul. .1 48/197 l M Brook, NJ. Primary Examiner-Meyer Perlm Filed: 1973 Assistant ExaminerRonald C. Capossela [21] APP] 387,173 Attorney, Agent, or FirmEvelyn Berlow 52 US. Cl. 62/48, 48/197 FM, 252/372 [57] ABSTRACT [51 Int. Cl. F17d 11/00 Acetylene and ethane are blended to f ix [58] Field of Search 62/48; 48/197 FM; 252/372; that are safe toward deflagration under any conditions 44/52 of compression. The blends are then compressed and condensed to form liquids that can be safely stored, [56] References Cit d transported,'and used as a source of acetylene in UNITED STATES PATENTS Chemlca reacmns- 1,096,797 5/1914 Snelling 62/48 3 Claims, 1 Drawing Figure ACETYLENE (j ACETYLENE/ETHANE LIQUID MIXQU RE /2 /3 j A} o 6) O ANE STORAGE ETH l TANK PATENTED JANZI I975 TANK STORAG E ACETYLEN E /ETHANE LIQUID MIXTURE PROCESS FOR SAFE STORAGE, HANDLING, AND USE OF ACETYLENE This invention relates to a method for the safe handling, storage, and use of acetylene.

Acetylene is an energy-rich, highly-reactive compound that is an intermediate in the manufacture of such important industrial compounds as acetaldehyde, vinyl chloride, vinyl acetate, acrylonitrile, and chlorinated ethylenes.

Because of the well-known hazards of working with compressed acetylene on a large scale, most of the early work on the reactions of acetylene was directed toward those reactions that can be conducted at essentially atmospheric pressure. The study of the chemistry of acetylene received a great impetus from the work of W. A. Reppe and his group on the high pressure reacll, methane, ethylene, and propane, which have previously been suggested as diluents for acetylene, do not share this property, and they have critical temperatures that are quite different from those of acetylene and ethane.

When acetylene is separated from the acetylene ethane mixtures of this invention by chemical reaction,

a fail-safe condition results as the unreacted material becomes richer in ethane, thereby assuring a safe concentration of the deflagration suppressor. Because e'thane is inert under all reaction conditions for acetylene, its presence in the reaction mixture does not give rise to side reactions. Following its use as deflagration suppressor in mixtures with acetylene, ethane can be recovered and reused, or it can be used as a fuel at the reaction site. In addition ethane is low in cost and readily available in most industrial areas.

Table l Vapor Temperature at Indicated Pressure Pressure (Atmospheres) Methane Ethane Ethylene Acetylene Propane It) 32.0 52.s -32.7 -5

l00 +101) l4.2 +4.x

tions of acetylene. The resulting intense interest in Table II acetylene chemistry has resulted in a considerable amount of research to discover means that will reduce the Critical Temperature Critical Pressure risk in handling acetylene under pressure. (Alnwsphsm) Two general methods are used to minimize the dan- Methane 46 ger of explosive decomposition of acetylene under Ethane 32.3 4x2 pressure. One method involves diluting the acetylene ,Z'g with an inert gas, such as nitrogen or carbon dioxide. Propane 16 43.0 The second involves designing the apparatus so as to avoid any large free space in the system, for example, by using small bore lines for carrying acetylene feeds or by packing the lines and vessels with steel tubes or Raschig rings. In addition, the apparatus is generally built to withstand pressures at least about twelve times the operating pressure since the energy of deflagration of acetylene is enough to increase the system pressure about elevenfold. These methods are not completely satisfactory because they leave the acetylene in an unstable condition in which deflagration will occur in the presence of an ignition event.

In accordance with this invention, it has been found that acetylene can be blended with ethane to form mixtures that can be stored, transported, and used at high pressures without danger of deflagration. These mixtures which contain up to about 40 mole percent of acetylene cannot be exploded no matter how high the temperature or pressure or how violent the initiator is used.

Ethane has an unusual combination of properties that makes it an exceptionally valuable diluent for acetylene. In addition to its exceptional ability to suppress deflagration of acetylene, ethane has the further advantage that its relative volatility is very close to that of acetylene over all ranges of temperature. Because acetylene-ethane mixtures can be separated only by multiple-stage, low temperature rectification processes, there is no danger of inadvertent physical separation of ethane from the acetylene. As is shown in Tables I and In the practice ofthis invention, acetylene is blended with ethane under low pressure to form mixtures that contain about 20 to 49 mole percent of acetylene and 60 to 80 mole percent of ethane, and preferably about 30 to 35 mole percent of acetylene and 65 to mole percent of ethane. The mixtures are compressed to high pressure and then stored as a liquid or used as a source of acetylene for chemical reactions.

The conditions under which the mixtures are prepared are not critical. In most cases the acetylene and ethane are blended at a temperature between about 20 and 50C. and a pressure between about 1 atmosphere and 3 atmospheres. It is generally preferred to form the mixtures at ambient temperature (25C.) at a pressure of 1.1 to 2 atmospheres. The resulting mixture is compressed to about 5 to 200 atmospheres, preferably 10 to 50 atmospheres and used as a source of acetylene for chemical reactions or condensed to a liquid stage for transportation and storage.

The invention is illustrated by the following examples.

EXAMPLE 1 The preparation and storage of an acetylene-ethane mixture are shown schematically in the drawing. Acetylene and ethane at ambient temperature (25C.) and at a pressure of 8 psig are mixed in the ratio of 35 moles of acetylene to 65 moles of ethane as they flow from their supply manifolds l0 and 11, respectively, into compressor line 12; The gas mixture is fed into multistage compressor 13 where it is compressed to 200 psig. It is then fed into a liquid ammonia refrigerated heat exchanger 14 in which it is liquefied at 23C. The liquid acetylene-ethane mixture is pumped through pump 15 to storage tank 16 at 200 psig and stored at this pressure.

The acetylene-ethane mixture in the compressor line 12 flows past a continuous infrared monitor 17 which shuts down the compressor 13 as soon as a mixture containing more than about 35 mole percent of acetylene appears in the compressor line.

EXAMPLE 2 A. Butynediol is produced industrially by a process in which acetylene and aqueous formaldehyde 12% CH O) are passed concurrently at a pressure of 5.0 to 5.5 atmospheres and a temperature of 90100C. over a copper acetylide catalyst on granular silica gel. The excess acetylene is recovered and recycled. The liquid product, which contains about 30 percent of butynediol, is distilled to separate unreacted formaldehyde and propargyl alcohol from the butynediol.

This reaction between acetylene and formaldehyde is slow and inefficient. The conversion of acetylene to butynediol is about 50 percent. The space-time yield is only 1.0 kg. of butynediol per liter of catalyst per 24 hours. Because the acetylene is in a deflagrating condition, the reaction must be carried out in process equipment that is built to withstand a maximum pressure of 1,000 atmospheres (14,700 psia).

B. When the acetylene used in the foregoing process for the production of butynediol is replaced by the nondeflagrating acetylene-ethane mixture whose preparation and storage are described in Example 1, the reaction with formaldehyde can be carried out safely at a pressure of atmospheres (1,470 psia). At this pressure, the reaction takes place rapidly, and there is a substantially higher conversion of acetylene to butynediol.

The replacement of acetylene by an acetylene-ethane mixture makes it possible to carry out the process at an appreciably higher pressure and thereby increase the capacity of a plant by 300 percent or more. Alternatively, the process using the acetylene-ethane mixture can be carried out in smaller, less costly processing equipment since the equipment need withstand a maximum pressure of about 200 atmospheres, rather than the maximum pressure of 1,000 atmospheres that may be encountered when acetylene in a deflagrating condition is present.

What is claimed is:

l. The process of storing and handling acetylene at high pressures without danger of dellagration that comprises the steps of a. mixing acetylene with ethane at a temperature in the range of 20 to 50C. and a pressure in the range of 1 atmosphere to 3 atmospheres, thereby forming a gaseous mixture that contains up to 40 mole percent of acetylene,

b. subjecting said gaseous mixture to a pressure in the range of about 5 to 200 atmospheres, and

c. cooling the compressed gaseous mixture to liquely 2. The process of claim 1 wherein step (a) acetylene is mixed with ethane at ambient temperature at a pressure in the range of 1.1 to 2 atmospheres.

3. The process of claim 1 wherein in step (b) the ace tylene-ethane mixture is compressed to a pressure in the range of 10 to 50 atmospheres.

Patent No. 3, 61,160 Da d Jan. 21, 1975 Inventor(S) David G. Walker It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 44, change "49" to 40 Column 3', line 16, insert before "12%" v Signed and sealed this 11th day of March 1975.

(SEAL) Attest:

. C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM PO-1050 (IO-69) USCOMM-DC 60376-P69 v: v.5. eovznmazm' PRINTING OFFICE 19:9 o-ass-szu, 

2. The process of claim 1 wherein step (a) acetylene is mixed with ethane at ambient temperature at a pressure in the range of 1.1 to 2 atmospheres.
 3. The process of claim 1 wherein in step (b) the acetylene-ethane mixture is compressed to a pressure in the range of 10 to 50 atmospheres. 